Exam 2 - T Cells - Receptors, MHC, and Antigen Recognition

Question 1

What is the main function of CD8 T cells?

Answer 1

Kill virus-infected cells

Question 2

What is the function of CD4 T1 cells?

Answer 2

Activate infected macrophages

Provide help to B cells for antibody production

EXTRACELLULAR BACTERIA

Question 3

What is the function of CD4 T2 cells?

Answer 3

Provide help for B cells for antibody production, esp switching to IgE

Helminth parasites

Question 4

What is the function of CD4 T17 cells?

Answer 4

Enhance PMN response

PROMOTE BARRIER INTEGRITY - MUCOSAL SURFACES

Question 5

What is the fx of all types of T cells?

Answer 5

B cell help

Isotype switching

Antibody production

Question 6

What is the fx of CD4 regulatory T cells?

Answer 6

Suppress T cell responses

Question 7

What do TCRs (T Cell Receptor) bind?

Answer 7

Polypeptides

Question 8

Where are TCRs expressed?

Answer 8

On cell surfaces, never secreted

Similar in structure to immunoglobulins

Interacts with MHC presented antigen

Question 9

What are the 2 classes of TCRs?

Answer 9

Alpha:Beta T Cells

Gamma:Delta T Cells

Question 10

Tell me about Alpha:Beta T Cells.

Answer 10

• Develop and mature in the thymus
• “Classic” T cell
• Adaptive immunity
• Common in CIRCULATION, not tissues
• Positive and negative selection

Question 11

Tell me about Gamma:Delta T Cells.

Answer 11

• Not involved in adaptive immunity
• Monitor tissue health
• Common in TISSUES, not circulation
• DEVELOPS, but does not mature in the thymus
• Limited positive and negative selection

Question 12

T/F - T cells only express one type of TCR class, NEVER both.

Answer 12

TRUE

Question 13

CD4 T1 take care of what?

CD4 T2 take care of what?

CD4 T17 take care of what?

Answer 13

T1 - Small, extracellular

T2 - Big, multicellular

T17 - Mucosal

Question 14

T/F - TCR genes undergo rearrangement.

Answer 14

TRUE

Question 15

The alpha chain has what segments on it?

Answer 15

V, J, and C segments with junctional diversity

V = Variable
J = Junctional
C = Constant

Question 16

The beta chain has what segments?

Answer 16

V, J, D, and C segments with junctional diversity

D = Diversity

Question 17

TCRs req the ______ complex for signal transduction.

Answer 17

CD3

It mediates TCR signaling, and expression does NOT occur w/o CD3

Question 18

What fragment is the TCR associated with in signal transduction?

Answer 18

Zeta fragment

Question 19

What does MHC stand for?

Answer 19

Major histocompatibility complex

Question 20

What are the two classes of MHC?

Answer 20

I

II

Question 21

What antigen does MHC class I target and what cells have MHC I?

Answer 21

Intracellular antigen

Nearly all cells have it

Question 22

What parts make up the MHC class I?

Answer 22

Alpha chain (alpha 1,2, and 3)

Beta 2 microglobulin

Question 23

What type of antigen loading happens with MHC class I?

Answer 23

ER antigen loading

Question 24

CD__ communicates with MHC Class __, while CD__ communicates with MHC Class __.

Answer 24

CD8 - MHC Class I

CD4 - MHC Class II

Question 25

MHC Class II targets when antigen type and what cells have MHC II?

Answer 25

Internalized antigen Antigen presenting cells - B cells - Macrophages - Dendritic cells

Question 26

What chains are in MHC Class II?

Answer 26

Alpha and beta chains

Question 27

Which type of antigen loading does MHC II do?

Answer 27

Vesicular ER loading

Question 28

CD8 receptor binds which domain on MHC Class I?

Answer 28

Alpha3

Question 29

The CD4 receptor binds what domain on the MHC II molecule?

Answer 29

Beta chain

Question 30

What does the beta 2 microglobulin do for the MHC Class I molecule?

Answer 30

Stabilizes the molecule

Question 31

In general, both MHCs do what?

Answer 31

Bind peptides for TCR presentation They are promiscuous, not particular at all Nearly all cells express some form of MHC -RBCs are devoid of MHC

Question 32

The following are hematopoietic cells. Which are MHC I and which are MHC II? ``` T cells B cells Macrophages Dendritic cells Neutrophils Erythrocytes ```

Answer 32

T cells - I B cells - I and II Macrophages - I and II Dendritic cells - I and II Neutrophils - I RBCs - NONE

Question 33

The following are non-hematopoietic cells and they all express what type of MHC Class? Hepatocytes Kidney epithelium Brain

Answer 33

MHC Class I

Question 34

Tell me the process of MHC Class I antigen presentation.

Answer 34

Intracellular antigen Proteasome - Antigen broken down to peptides here Peptides transported to ER Peptide bound by MHC Class I MHC Class I present peptide at cell surface

Question 35

Tell me the MHC Class II antigen presentation.

Answer 35

Extracellular antigen Endocytosis vesicle Peptides produced in phagolysosome MHC Class II comes vesicled from ER and meets with phagolysosome Peptides are bound to MHC Class II w/in phagolysosome MHC Class II presents peptide at cell surface

Question 36

Tell me the detailed version of MHC I antigen loading in the ER.

Answer 36

MHC Class I heavy chain is stabilized by CALNEXIN until beta2-microglobulin binds CALNEXIN is released and a complex of calreticulin, tapasin, ERp57, and TAP forms. A peptide is delivered by TAP to the heavy chain - this forms the “mature” MHC Class I molecule MHC Class I dissociates from the complex and is exported from the ER to the cellular surface

Question 37

MHC I - Antigen Loading in the ER allows for what?

Answer 37

Peptides trimmed before expression Allows detection of intracellular infection Intracellular peptides are 8-10 residues

Question 38

T/F - Crosspresentation of endocytosed antigen is just that internalized antigen is expressed on MHC Class I and MHC Class II.

Answer 38

TRUE This is important in naive CD8 T cell activation

Question 39

Tell me the detailed version of MHC II - Antigen Loading into vesicles.

Answer 39

Antigen is taken from the extracellular space into intracellular vesicles Early endosomes have neutral pH, and endosomal proteases are inactive Acidification of vesicles activates proteases to degrade antigen into peptide fragments Vesicles containing peptides fuse with vesicles containing MHC Class II molecules

Question 40

What prevents self antigen presentation?

Answer 40

CLIP

Question 41

Tell me the detailed version of what CLIP does.

Answer 41

INVARIANT CHAIN blocks binding of peptides to MHC Class II in ER Invariant chain is cleaved off in vesicles, but the CLIP portion of the invariant chain remains bound CLIP blocks binding of peptides to MHC Class II HLA-DM facilitates release of CLIP, and peptides bind

Question 42

What is CLIP?

Answer 42

Class II-associated invariant chain peptide

Question 43

What dictates MHC specificity?

Answer 43

Co-receptors *This is within the T Cell Synapse

Question 44

What happens when a CD8 T cell contacts a virus infected cell?

Answer 44

It leads to apoptosis

Question 45

What happens when a CD4 T cell contacts a macrophage?

Answer 45

Cytokines released and those activate a macrophage to release their own cytokines

Question 46

What happens when CD4 T cells contact B cells?

Answer 46

Cytokines are released and B cells differentiate into plasma cells, and then antibodies are released from the plasma cell